Animal feedstuffs include forages such as cereal grains, whole cereal crops, grasses, legumes, rice, alfalfa, lucerne, sorghum and hay. The forage is usually stored as a dried material, or in the form of a silage produced from these materials by fermentation processes. This fermentation to produce silage is generally conducted in an oxygen-free environment and in the presence of acid-producing bacteria. The dried material or the silage is taken for use as feedstuff as needed.
When a forage is to be stored as a dried material, it is necessary that the material be dried to varying degrees prior to storing in order to minimize the colonization of harmful microbes naturally present. For example, hay in the field carries a complex population of fungi, yeasts, actinomycetes and bacteria which could colonize during storage and lead to, in extreme cases, spontaneous combustion. Also, the development of mould or fungus can lead to palatability and health problems for both animals and humans. The rate of microbial development varies depending upon the moisture content, and for baled hay a moisture content of about 15% is a generally preferred upper limit where microbial activity is reduced to a tolerable level. In North America, in order to achieve this low level of moisture content, the usual practise is to allow a period of field wilting or drying prior to baling.
Silage is the fermentation product of crops, such as those listed hereinbefore, brought about by native lactic acid-producing bacteria present on the crop at harvesting. Lactic acid fermentation can be improved by the addition of selected lactic acid-producing bacteria. Such bacteria include selected lactic acid-producing strains of the genus Lactobacillus, the genus Streptococcus, the genus Enterococcus, the genus Lactococcus and the genus Pediococcus.
It is important that a state of anaerobiosis be attained in order to obtain good silage, and therefore, the crop is usually stored and permitted to ferment in a sealed container or silo. The state of anaerobiosis, however, can be difficult to achieve rapidly, and is governed by the degree to which air comes into contact with the preserving material in the silo. The exposure of silage to air, in particular oxygen in the air, results in spoiling of the silage, and the degree of spoiling will depend on the aerobic stability of the silage. Also, silage material can spoil after having been removed from the silo prior to animal feeding depending upon this elapsed time interval. In these instances, the spoiling is primarily due to yeast or mould contamination of the ensiled material.
Fungal growth in forage can be modified or prevented by the addition of chemical fungicides, such as ammonia or organic acids or their salts, prior to storing, or by various physical means including longer wilting periods in the field, the use of driers, reduction of the oxygen concentration, and/or alteration of pH.
A bacterial strain of the species Bacillus subtilis has been disclosed in SU 751382, dated Jul. 30, 1980, to display fungicidal activity in fodder specifically against Stachybotris alternans and Dendrodochium toxicum.
U.S. Pat. No. 4266028, dated May 5, 1981, discloses the preparation of the anti-fungal antibiotic prodigiosin by cultivation of the bacterium Serratia marcescens R-2.
It would be required that any specific biological control agent for use in silage or dried forage would have to operate under a complex set of changing conditions and compete with the natural microflora that are present.
Surprisingly, we have now found bacterial strains that can be used for effectively controlling the growth of fungi, actinomycetes and bacteria in forage. These bacterial strains are mixed with lactic acid-producing bacterial strains for use in producing and preserving silage. In particular, we have found bacterial strains of the genus Serratia that exhibit both anti-fungal and anti-bacterial properties enabling the biological control of several moulds and bacteria in forage.
Therefore, it is an object of the present invention to better prepare and preserve silage by treatment of a suitable material to be ensiled with a mixture of an anti-fungal bacterial strain and a lactic acid-producing bacterial strain.
It is a further object of the present invention to provide anti-fungal bacterial strains that may be used in permitting hay or other dry forage to be baled or stored (preserved) at significantly higher moisture content than normal.
It is yet a further object of the present invention to provide bacterial strains that may be formulated into compositions for use in treating forage.